It is a measure of randomness.

A theater full of people has a relatively low entropy. Everyone is sitting in even rows and most of them are facing the front, and relatively still. The same number of people in a crowded city square has a relatively high entropy. The people are much less ordered in their position - there are some groups, some people out on their own, they are all facing different directions and moving at different speeds and in different directions.

A theater full of businessmen has a lower entropy than a theater full of businesswomen. The businessmen are mostly wearing dark suits with a colorful tie. The businesswomen are competing with all manner of colors dresses and business suits.

And at the risk of being macabre, a living human has a lower entropy than a dead one. A living human's molecules are carefully grouped into cells, cell nuclei, DNA strands and the like. A decaying corpse has molecules every which way.

The second law of thermodynamics says that entropy in a closed system (nearly) always increases.

This is often used by religious people to try to disprove the theory of evolution (Selfish Gene Theory) because living things have a higher entropy that dead things, therefore the creation of life breaks the laws of physics, and hence must be done by God. Invariably when this argument is used, they lose the 'in a closed system' part of the law. If a living thing is observed within its environment, total entropy generally has actually increased.

It is a disturbing argument - not because it is true (it's rubbish), but because it is so popular. The people who try this argument on a physicist don't know any better - they believe what they are saying. However these people did not make this up themselves. They have clearly been told this argument by more knowledgable people in their churches - who presumably know they are lying to their own group. It is amusing to see religious organisations take the moral high-ground on issues when they are so dishonest in the programming they give their own followers.